Here we have a stunning, all original, circa 1948 Rolex Oyster Perpetual Chronometer ‘Bubbleback’ reference 3131. It has the 32.5mm 14k light rose gold tone case, designed for the American market. 
 
The Rolex Oyster bubbleback is a watch that has long had a committed following, and for good reason. They represent classic and elegant styling, equally at home in sporty or dressier settings. They ooze sophistication with all the benefits of Rolex’ famous waterproof patents. The combination results in an instantly recognisable classic, with the screw down Oyster crown jutting out proudly from the side. The depth of the case back is also synonymous with the model, to house the automatic movement. 
 
What is not often noted by collectors is that they were one of the most heavily altered models, due to their early popularity amongst collectors in the 1980s and 1990s. The elusive and desired California dial variations and lack of care for originality, led to many having older dial restorations. That is why un-tampered models such as this, are a wonderful find. 
 
Despite its compact width, the watch has significant presence on the wrist due to its lug design and length, as well as the width of the case with the screw down Oyster Patent crown. 
 
The original dial is in excellent, lightly aged condition. It has the eye catching raised three-dimensional gold tone Arabic numerals, with the gold tone raised dot minute markers to the exterior. These provide a depth and intrigue to the dial which makes it a joy to look at. 
The dial is a silver satin base tone with the lightly grained finish and light spotting with age. It is signed with the Rolex cornet and the ‘Rolex Oyster Perpetual’ text. It is also marked with the ‘Officially Certified Chronometer’ text above 6 O’clock with the ‘Swiss Made’ signing to the foot of the dial. 
 
The hands are wonderful, in the Lance Alpha style, matching the tone of the numerals. A neat contrast is provided by the thermally blued central second hand with the lollipop counterbalance. 
 
The case has the broad bevelled bezel with the polished finish. The front and sides of the case also have the polished finish. There is an eye-catching contrast provided by the central block between the lugs which has the brushed finishing. The reference and serial number signing between the lugs is well defined. To the right is the original ‘Rolex Oyster’ signed crown. The rear of the case has the brushed finish, with the Swiss hallmark clearly visible. The famous bubble back has the coin edge with the polished finish to the face. Inside it is marked with the Rolex signing and the Swiss hallmarking for 14k gold. It has the Swiss key mark for Genex, who produced beautiful gold cases for Rolex since the early 1940s. It is signed with the reference 3131, as well as the 3130 marking. 
 
The movement is the chronometer grade calibre 630, which is an automatic movement. The automatic module is the reason for the birth of the ‘bubbleback’, which was necessary to house the depth of the movement. It has been recently serviced and is keeping time to within +25 seconds variation a day.
 
Please see the images as these compliment and aid the description provided below.
A further condition report is below.
 
Dial: 
The dial is original and is in excellent, lightly aged condition. It is a silver satin basin tone with a light brushed finish. It has the black signing to the dial which is in good, unworn condition. The raised three-dimensional gold tone Arabic numerals and raised dot minute markers are good.
 
Hands: 
The hands are of Lance Alpha and are original. They are in good condition with an even gold tone. The central second hand is also original and good, with the thermally blued finish.
 
Glass: 
The crystal is a good acrylic replacement which is in good condition.
 
Crown: 
The gold tone crown is original and has the Rolex cornet logo. It is in good condition and screws down well. It has some wear to the rose gold tone, with the yellower tone underneath exposed.
 
Case:
The case is 14ct gold and is in good condition for the age. The tone of the gold is good and even, in a light rose tone. It has been lightly polished to a high standard in the past to restore the finishes with the brushing between the lugs. There are some light surface scratches. The reference and serial numbers between the lugs are good and clear.
 
Caseback:
The Oyster coin edge screw back is formed of 14ct gold and is in good condition for the age. It has the well-defined coin edge, with a polished face. It has light scratching associated with age. Inside the engravings are good and clear. It has some scoring from the rotor having rubbed against the case in the past.
 
Strap: 
The watch is presented on a new Hirsch strap which is a great match. It has a gold plated Rolex buckle with the cornet logo, which is later, from the 1960s. 
 
Movement: 
The movement is the Rolex calibre 630, which is chronometer grade. It was Rolex’ first automatic movement, introduced in 1931. It also has a Breguet hairspring and benefits from detached manual wind. 
 
It has been recently serviced. It’s keeping time to within +25  seconds a day, with an amplitude of 250 degrees and a beat error of 0.5m/s.
 
Case dimensions: 
Case width: 32.25mm
Case width with crown: 35mm 
Case length: 32mm 
Case length lug to lug: 39.3mm
Case Depth: 13.5mm
Lug width: 17.5mm